One major concern when crafting our bespoke wooden window frames is the ‘movement’ of the timber that we use in construction. Typically timber falls into one of three categories – large, medium or small, movement – which determines the amount that the wood will move when it absorbs moisture from the air. This can cause problems such as warping and cracking depending on whether the wood becomes too wet or too dry.
Although we can take steps to minimise the impact of water absorption, through various practices such as drying the timber and treating it with coats of paint and varnish, wood is a hygroscopic material and will always seek to reach equilibrium with the moisture content of its environment. As such we use the technique of multi-layering in order to compensate for the wood’s natural tendency to expand and contract.
In this practice, at least three layers of timber are glued together with their grains set in opposing directions. This not only reinforces the strength of the wooden frame but helps to counteract the swelling of wood as it takes on water.
As timber becomes more humid water begins to fill up the cavities between its cells, thus causing these cavities and the timber to expand. When this expansion occurs concurrently in layers of multi-layered wood, which have their grain in opposing directions, the moisture movement of the water is evened out, thus preventing the warping that you would otherwise find in single layered timber constructions.
This is by no means a new technique and has been employed throughout the ages to create wooden structures that needed to be particularly resistant to potential water damage. For years multi-layered timber has been used in the UK to create bridges, roofs, stadiums and other high-demanding span timber structures. In fact, throughout Europe, it has been used to create door and window frames for a long time as well, though the technique is just now being utilised in the UK for its longevity and sturdiness.
The advantages of using this type of engineered timber are much fold, though the top of the list is its potential in terms of design. Multi-layered timber is effectively man-made, it retains the natural product’s positive qualities including aesthetic and ecological sustainability, whilst accruing the advantages of being far more reliable and easy to work with.
The timber can be designed to meet application-specific requirements far easier than solid wood can be, and so window frame designs have become smarter and intuitive, without having to account for the twisting and warping that will occur in solid wood designs. This means that we can create more intricate and spectacular bespoke wooden window frames, which not only work around the environment they are placed in, but also offer an increased guarantee of durability.